For some time I've been using a custom-made function for
emms-track-description-function with the vlc player. Recently I started
using the mpv player with EMMS and with that my custom function causes
an error every time a track is read, exemplified by the following
backtrace:
Debugger entered--Lisp error: (json-readtable-error 61)
json-read()
json-read-from-string("=====================================================================================")
emms-player-mpv-ipc-recv("=====================================================================================")
emms-player-mpv-ipc-filter(#<process emms-player-mpv-ipc>
"{\"event\":\"playback-restart\"}\n")
My custom function adds lines to the playlist buffer that lack the
emms-track property, and apparently the mpv backend does not handle
these. I've worked around the error with the following advice:
(advice-add #'emms-player-mpv-ipc-recv :before-while
(lambda (s) (string-match "^{" s)))
I don't know if this error is due to a bug in the mpv backend or if my
custom function is unsupported. If the latter, it would be helpful to
document the expected format. If this is really a bug in the mpv
backend, replacing the above advice with the attached patch prevents the
error for me, but I know nothing about the implementation of the mpv
JSON IPC interface, so there is probably a better fix.
Steve Berman
diff --git a/emms-player-mpv.el b/emms-player-mpv.el
index 4b7b908..1683380 100644
--- a/emms-player-mpv.el
+++ b/emms-player-mpv.el
@@ -651,19 +651,20 @@ errors, if any."
Only used with JSON IPC, never called with --input-file as
there's no feedback there."
(emms-player-mpv-debug-msg "json << %s" json)
- (let*
- ((json-data (json-read-from-string json))
- (req-id (alist-get 'request_id json-data))
- (ev (alist-get 'event json-data)))
- (when req-id
- ;; Response to command
- (emms-player-mpv-ipc-req-resolve req-id
- (alist-get 'data json-data)
- (alist-get 'error json-data)))
- (when ev
- ;; mpv event
- (emms-player-mpv-event-handler json-data)
- (run-hook-with-args 'emms-player-mpv-event-functions json-data))))
+ (when (string-match "^{" json)
+ (let*
+ ((json-data (json-read-from-string json))
+ (req-id (alist-get 'request_id json-data))
+ (ev (alist-get 'event json-data)))
+ (when req-id
+ ;; Response to command
+ (emms-player-mpv-ipc-req-resolve req-id
+ (alist-get 'data json-data)
+ (alist-get 'error json-data)))
+ (when ev
+ ;; mpv event
+ (emms-player-mpv-event-handler json-data)
+ (run-hook-with-args 'emms-player-mpv-event-functions json-data)))))
(defun emms-player-mpv-ipc-fifo-cmd (cmd &optional proc)
"Send --input-file command string for older mpv versions.
